1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.
In this specification, a semiconductor device means any device which can function by utilizing semiconductor characteristics, and an electro-optical device, a semiconductor circuit, and an electronic device are all included in the category of the semiconductor device.
2. Description of the Related Art
Attention has been focused on a technique for forming a transistor using a semiconductor thin film (also referred to as a thin film transistor (TFT)). The transistor is applied to a wide range of electronic devices such as an integrated circuit (IC) or an image display device (display device). A silicon-based semiconductor material is widely known as a material for a semiconductor thin film applicable to a transistor. As another material, an oxide semiconductor has been attracting attention.
A transistor including an oxide semiconductor is required to have excellent electric characteristics for application to semiconductor devices with higher performance. In order to achieve excellent electric characteristics of the transistor including an oxide semiconductor, a technique in which low resistance source and drain regions by an aluminum reaction method has been reported (e.g., see Non-Patent Document 1).
For example, a transistor whose active layer includes an amorphous oxide including indium (In), gallium (Ga), and zinc (Zn) is disclosed (see Patent Document 1).